MDB, ok, so you're not the typical family situation. Since it appears you have the ability and plan to "vacation" much more than most, and have a large family, my recommendation is get a motorhome and tow a toad when you want or need to. Heck you can even drive a second vehicle when you want or need to since you have 3 drivers.
Budget wise, you'll have to shop carefully, but the right time of year is coming up in the NE and NW to buy an RV. Example: A friend found a 30' Class A last year. Older, 03 or something, little sun faded but otherwise good shape, well maintained, 25k miles V10 for $12k if I remember right. Tows an enclosed trailer with bike or a Jeep with it. I've driven it, goes down the road nice at 75mph. He's probably got another $2-3k in it for tires, stereo, service work etc and some time.
The key to being somewhat economical with older used vehicles, as you'r probably aware is you have to be willing and able to spend some time on fixin and upkeep and not be hauling it to the shop for every little repair.
Good luck in you search!